This is King Richard's Well where, legend has it, Richard III drank before the Battle of Bosworth. You can find it close to Shenton station on the Battlefield Line.
The plaque reads:
Near this spot, on August 22nd 1485, at the age of 32, King Richard III fell fighting gallantly in defence of his realm & his crown against the usurper Henry Tudor.
The Cairn was erected by Dr. Samuel Parr in 1813 to mark the well from which the king is said to have drunk during the battle.
It is maintained by the Fellowship of the White Boar."Near this spot" may be optimistic: modern scholarship place of the battle a mile or so to the south west of Shenton and the Battle of Bosworth visitor centre.